AC generator for an automotive vehicle with enhanced cooling of internal elements

ABSTRACT

A cooling fin is fixed to a frame and mounts a plurality of rectifying elements. The cooling fin is configured into a circular ring shape separated at a cutout section. A brush holder, a connector casing and an IC regulator are disposed in this cutout section. A circumferential gap of the cutout section is smaller than three times a circumferential width of the brush container.

This is a now U.S. Pat. No. 6,060,802 division of Application No.09/035,814, filed Mar. 6, 1998.

BACKGROUND OF THE INVENTION

The present invention relates to an AC generator (i.e., also-calledalternator) for an automotive vehicle, which is preferably installed ina passenger vehicle or a truck or the like.

To reduce the aerodynamic resistance while traveling, vehicle body tendsto be formed into a slant nose shape. Securing a sufficient space for apassenger compartment is of great concern. To satisfy theserequirements, engine rooms of automotive vehicles have been becoming sonarrow and crowded such that now only a limited amount of space isavailable for instaling an AC generator. Meanwhile, to improve fueleconomy, rotation of an engine tends to be decreasing. Correspondingly,rotation of the AC generator is lowered. On the other hand, there is aneed to increase the electric load for safety control devices etc. Thus,improving the generating performance of the AC generator is stronglyrequired. In other words, a compact, powerful, and non-expensiveautomotive AC generator is required.

To this end, the power output may be increased by reducing the windingresistance and air gaps or by increasing an exciting current. However,this will induce heat generation at various components constituting theAC generator. Especially, rectifying elements (i.e., diode) aresubjected to a large temperature increase. The rectifying elements aregenerally used to rectify electric power when generated by a stator fromAC voltage into DC voltage. To secure the reliability of this rectifyingelement, it is necessary to cool the cooling fin satisfactorily within alimited space. To improve the cooling performance, it is of coursepossible to enlarge the cooling fan so as to increase an amount ofcooling air. However, solely increasing the cooling air volume willresult in an increase of noise.

FIG. 4 shows an automotive AC power unit for a conventional automotiveAC generator.

Cooling fins 511 and 512, used for cooling the rectifying elements, aredisposed on a rear frame. An IC regulator 7 and a connector casing 8 aredisposed at point-symmetrical positions with respect to the cooling fins511 and 512, respectively. A brush holder 6 is disposed at a portionsurrounded by them. An appropriate clearance is provided at aradial-inner end and a radial-outer end of each of the cooling fins 511and 512. More specifically, as shown in FIG. 5, the radial-inner end ofeach cooling fin 511 or 512 is spaced from a slip ring protector 91 witha radial clearance while the radial-outer end is spaced from a rearcover 92 with another radial clearance. The cooling fins 511 and 512have circumferential ends which are partly brought into contact withneighboring components so as to provide open spaces 93.

A central portion of each of the cooling fins 511 and 512 issufficiently cooled by cooling air, as the cooling air is introducedfrom an opening provided on the rear cover 92 and flows along thesurfaces of these cooling fins 511 and 512, as shown in FIG. 5. However,the cooling air does not flow at the above-described contacted endportions of the cooling fins 511 and 512. Meanwhile, the cooling airflow resistance is lowered significantly at the opened end portions ofthe cooling fins 511 and 512, compared with other portions wherecomponents are disposed. Thus, the introduced cooling air may directlygo out through the opened end portion without interacting with thecooling fins 511 and 512. Accordingly, cooling performance is notuniform among a plurality of diodes 513 and 514 arranged in acircumferential direction on the cooling fins 511 and 512. Morespecifically, the diodes 513 and 514 positioned at the circumferentialends of the cooling fins 511 and 512 are not satisfactorily cooled bythe cooling air, compared with the diodes 513 and 514 positioned at thecircumferential centers of the cooling fins 511 and 512.

U.S. Pat. No. 4,952,829 discloses a cooling fin for a rectifying elementwhich has a sectorial opening at a radial-outer end of a brush holder.This arrangement will encounter with the above-described problem thatthe rectifying elements positioned near the opening are not sufficientlycooled because the cooling air is directly guided to the opening.

SUMMARY OF THE INVENTION

In view of the foregoing problems encountered in the prior art, thepresent invention provides an automotive AC generator which is capableof improving the cooling performance of rectifying elements in a crowdedspace accommodating a brush holder, an IC regulator and a connectorcasing by increasing an effective cooling area of a cooling fin whileadequately maintaining the cooling performance of other components.

In order to accomplish the above-described and other related objects,the present invention provides a novel and excellent automotive ACgenerator characterized by the following features. A cooling fin (511,512), fixed to a frame (42), mounts a plurality of rectifying elements(513, 514) rectifying a generated power. A brush holder (6) includes abrush container (62) accommodating a brush (61) and a brush containerfixing arm (63) supporting the brush container (62). A connector casing(8) has terminals (81) for inputting and outputting electric signalsfrom and to a vehicle electric apparatus. An IC regulator (7) adjusts anoutput value of the generated voltage. A circumferential width of the ICregulator is substantially identical to a circumferential width of thebrush container (62). The cooling fin is configured into a circular ringshape separated at a cutout section (52). The brush holder, theconnector casing and the IC regulator are disposed in the cutoutsection. And, a circumferential gap (B) of the cutout section is smallerthan three times a circumferential width (A) of the brush container.

According to the above-described arrangement, the brush holder, theconnector casing and the IC regulator are disposed in the cutout sectionof the cooling fin. This arrangement is advantageous in that the coolingfin for the rectifying element can be extensively provided along anentire circumferential region except for the brush holder. Not only theeffective surface area of the cooling fin is increased, but also thecooling air can flow uniformly and effectively along the entirecircumferential region. Thus, the cooling performance can be greatlyimproved.

The circumferential gap of the cutout section of the cooling fin has asensitive correlation with generation of useless cooling air. In otherwords, the circumferential gap of the cutout section gives a largeinfluence to the cooling performance of the rectifying elements locatedon the cooling fin, especially in the vicinity of the cutout section.

Hence, the inventors of the present invention have conducted a test tocheck the temperature increase in a rectifying element located in thevicinity of the cutout section of the cooling fin when a ratio B/A isvaried. According to a test result shown in FIG. 3, the temperature ofthe rectifying element can be effectively suppressed when the ratio B/Ais smaller than 3.

In addition, both the brush holder and the connector casing can besecurely fixed to the cooling fin by using shorter fixing arms. This isadvantageous in that fixing strength and vibration durability can beimproved for the brush holder and the connector casing.

Preferably, the circumferential gap (B) of the cutout section is in arange of 1.5 to 2.8 times the circumferential width (A) of the brushcontainer.

Preferably, the IC regulator (7) is connected to at least one of thebrush holder (6) and the connector casing (8) with a clearance so thatcooling air can flow along a surface of the IC regulator. With thisarrangement, it becomes possible to effectively cool the IC regulatorwhich is a beat generating member as well as the rectifying elements.

Preferably, the cooling fin comprises a positive-electrode fin (511) anda negative-electrode fin (512) arranged in parallel to each other via aninsulating member (516). In this case, the positive-electrode fin. is acooling fin attached to higher-voltage side rectifying elements whichserve as an upper arm of an ordinary three-phase full-wave rectifyingcircuit. The negative-electrode fin is a cooling fin attached to alower-voltage side rectifying element which serves as a lower arm ofthis three-phase full-wave rectifying circuit. This arrangement isadvantageous for the cooling air. The cooling air flows in an axialdirection from a rear side of an automotive AC generator in response toa revolution of the rotor (3). The cooling air can be smoothly conveyedto the cooling fins (511, 512). This makes it possible to cool thecooling fins effectively. Furthermore, the effective area of the coolingfins can be increased. Thus, the cooling performance can be greatlyimproved.

Preferably, a capacitor (85) is connected between power supplyingterminals (82, 82) of a rectifying circuit including the rectifyingelements, and the capacitor is disposed in the cutout section (52). Thisarrangement is advantageous in that wiring layout can be simplified.This makes it possible to remove ripple components from a DC outputvoltage generated from the rectifying circuit. Furthermore, no extraspace is required for the electric noise-reducing capacitor. Thus, theeffective area of the cooling fin can be adequately maintained.

Preferably, the IC regulator (7). has a one-chip integrated circuitarrangement including an integrally molded cooling fin (73). Thisarrangement is advantageous because no regulator casing is required and,as a result, the space for the regulator can be reduced significantly.Accordingly, the effective area of the cooling fin can be increased. Thecooling performance can be improved.

Reference numerals in parenthesis, added in the above description, showthe correspondence to the components disclosed in a later-describedpreferred embodiment of the present invention. Therefore, these numeralsare merely used for expediting the understanding to the presentinvention and not used for narrowly interpreting the scope of thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription which is to be read in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a partly cross-sectional view showing an automotive ACgenerator in accordance with a preferred embodiment of the presentinvention;

FIG. 2 is a front view showing the automotive AC generator shown in FIG.1 under a condition where both a rear cover and a sealing ring areremoved;

FIG. 3 is a graph showing temperature characteristics of a rectifyingelement used in the automotive AC generator shown in FIG. 1, obtained byconducting a test;

FIG. 4 is a front view showing a conventional automotive AC generatorunder a condition where both a rear cover and a sealing ring areremoved; and

FIG. 5 is a partly enlarged cross-sectional view showing an essentialpart of the conventional automotive AC generator shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be explainedhereinafter with reference to accompanied drawings. Identical parts aredenoted by the same reference numerals throughout the drawings.

As shown in FIGS. 1 and 2, an automotive AC generator 1 in accordancewith a preferred embodiment of the present invention comprises a stator2 acting as an armature and a rotor 3 acting as a rotary field. Frontand rear frames 41 and 42 cooperatively support the stator 2 and therotor 3. A rectifier 5 is connected to the stator 2 to rectify an ACpower generated in this AC generator 1. A brush holder 6 supports abrush 61 which supplies the field current to the rotor 3. An ICregulator 7 has a function of adjusting an output value of the generatedvoltage. A connector casing 8 has input and output terminals forinputting and outputting electric signals from and to a vehicle electricapparatus. A rear cover 92 is provided to close the rear end of the ACgenerator 1.

The rectifier 5 comprises a positive-electrode cooling fin 511, and anegative-electrode cooling fin 512. A plurality of positive rectifyingelement 513 are mounted on the positive-electrode cooling fin 511. Aplurality of negative rectifying elements 514 are mounted on thenegative-electrode cooling fin 512. A terminal base 515 and a distancesleeve 516 are provided between the positive-electrode cooling fin 511and the negative-electrode cooling fin 512. The terminal base 515 and adistance sleeve 516 are made of a resin insulating member so as toelectrically insulate the cooling fins 511 and 512. The terminal base515 accommodates a conductive member which supplies the AC voltagegenerated by the stator 2 to the rectifying elements 513 and 514.

The cooling fins 511 and 512 are made of heat conductive material, suchas copper. Each of the cooling fins 511 and 512 is configured into acircular ring shape which is opened or separated at a cutout section 52.A circumferential gap “B” of the cutout section 52 is smaller than threetimes a circumferential width “A” of a later-described brush container62. Preferably, the gap “B” is in a range of 1.5 to 2.8 times the width“A”, as understood from the temperature characteristics of therectifying element shown in FIG. 3 which shows the temperature increaseof the rectifying element in relation to the variation of the B/A ratio.A circumferential width of IC regulator 7 is substantially identicalwith a circumferential width of the brush container 62. These coolingfins 511 and 512 are securely fastened to the rear frame 42 via theterminal base 515 and the distance sleeve 516 by means of appropriatefastening members.

When the stator 2 generates an AC voltage, this AC voltage is convertedinto a DC voltage by the plurality of rectifying elements 513 and 514which are fixedly mounted on the cooling fins 511 and 512 by solderingor riveting. A slip ring protector 91 is interposed between a seal ring94 and the rear frame 42 so as to surround a slip ring. The seal ring 94is disposed at the center of an inner end face of the rear cover 92. Anappropriate clearance is provided at a radial-inner end and aradial-outer end of each of the cooling fins 511 and 512. Morespecifically, in a radial direction, the radial-inner end of eachcooling fin 511 or 512 is appropriately spaced from the slip ringprotector 91 while the radial-outer end is appropriately spaced from acylindrical inner wall of the rear cover 92.

The brush holder 6 comprises the brush container 62 accommodating thebrush 61 therein and brush container fixing arms 63 supporting the brushcontainer 62. The brush container fixing arms 63 are fixedly fastened tothe positive-electrode cooling fin 511 and the negative-electrodecooling fin 512. The brush container 62 is disposed in the cutoutsection 52 of the cooling fins 511 and 512.

The connector casing 8 comprises terminals 81 for inputting andoutputting electric signals from and to an electric device of thevehicle. The connector casing 8 is fixedly connected to the cooling fins511 and 512 by fixing arms 82. The fixing arms 82 have a function ofsupplying electric power to the IC regulator 7. The terminals 81 and thefixing arms 82 are integrally molded. A capacitor 85, used for reducingthe electric noise, is disposed behind the connector casing 8.Electrodes 851 of the capacitor 85 are electrically connected tointermediate portions of the molded fixing arms 82. The fixing arms 82,each made of a metallic member, are securely fastened to thepositive-electrode and negative-electrode cooling fins 511 and 512 ofthe rectifier 5. The capacitor 85 is disposed in the cutout section 52.

The IC regulator 7 comprises a plurality of external connectingterminals 71, an IC main body (not shown) and a cooling fin 73, whichare integrally molded. The IC regulator 7 is coupled with or bonded on aregulator support 86 which is located below the connector casing 8. Anappropriate clearance is provided between the IC regulator 7 and theconnector casing 8, so that cooling air passes along an upper surface ofIC regulator 7 and a bottom surface of the connector casing 8. Theconnecting terminals 71 are electrically connected by welding toterminal ends 87 protruding from the molded connector casing 8.Furthermore, an appropriate clearance is provided between the ICregulator 7 and the brush holder 6, so that the cooling air passes alonga lower surface of IC regulator 7 and an upper surface of the brushholder 6.

As shown in FIG. 1, an inner axial end of IC regulator 7 is positionedopposite to a blade 10 a of a cooling fan 10. An outer axial end of ICregulator 7 is positioned opposite to an opening 92 a of the rear cover92. Thus, cooling air introduced through the opening 92 a of the rearcover 92 smoothly flows in the axial direction of AC generator 1 alongthe upper and lower elongated surfaces of IC regulator 7 toward theblade 10 a of the cooling fan 10.

With the above-described arrangement, the brush holder 6, the ICregulator 7 and the connector casing 8 are accommodated in the slit-likecutout section 52 of the cooling fins 511 and 512. Thus, it becomespossible to increase the substantial surface areas of the cooling fins511 and 512, greatly improving the cooling performance. Furthermore, thecooling air can smoothly flow along the upper and lower surfaces of theIC regulator 7 which is a heat generating member as well as therectifying elements 513 and 514.

Furthermore, the capacitor 85 can be disposed behind the connectorcasing 8 (i.e., at a downstream side in the cooling air flow). Thisarrangement is advantageous because the effective surface area of thecooling fins 511 and 512 is not reduced and the cooling air is smoothlyconveyed to the stator 2.

According to the above-described embodiment, the radial-outer end of thepositive-electrode cooling fin 511 is positioned outward in the radialdirection than that of the negative-electrode cooling fin 512. However,when the cooling fins 511 and 512 are reversely arranged in the axialdirection, it is preferable that the radial-outer end of thepositive-electrode cooling fin 511 is positioned inward in the radialdirection than that of the negative-electrode cooling fin 512. It isalso preferable that the radial-inner ends of the cooling fins 511 and512 are differentiated or offset.

According to the above-described embodiment, the positive-electrodecooling fin 511 is provided adjacent to the rear frame 42. However, itis possible to dispose the negative-electrode cooling fin 512 adjacentto the rear frame 42. Furthermore, it is possible to bring thenegative-electrode cooling fin 512 into contact with the rear frame 42.The resin insulating member, interposed between the cooling fins 511 and512, can be replaced by an insulating sheet or the like. In this case,it becomes possible to shorten the axial length of the rear end portionof the rectifier 5.

This invention may be embodied in several forms without departing fromthe spirit of essential characteristics thereof. The present embodimentas described is therefore intended to be only illustrative and notrestrictive, since the scope of the invention is defined by the appendedclaims rather than by the description preceding them. All changes thatfall within the metes and bounds of the claims, or equivalents of suchmetes and bounds, are therefore intended to be embraced by the claims.

What is claimed is:
 1. An automotive AC generator including a fieldwinding, the generator comprising: a regulator configured for adjustingcurrent flowing in the field winding, the regulator having a largestflat surface among other surfaces of the regulator, the largest flatsurface extending in an axial direction of the generator and adapted forpermitting cooling air to flow along the largest flat surface in theaxial direction; a connector casing positioned in the vicinity of theregulator and including a terminal exposed to an outside portion of thegenerator, the terminal being configured for transferring electricsignals between the generator and an electric device installed on anautomotive vehicle; a capacitor disposed adjacent to the connectorcasing and configured for reducing electric noise associated with theregulator, the capacitor and the connector casing aligning in the axialdirection of the generator, wherein the regulator extends parallel to analigning direction of the capacitor and the connector casing, theregulator is disposed radially outward of a brush container of a brushholder, so as to provide an axially extending cooling air passagebetween the regulator and the brush container, and the regulator, thecapacitor, and the connector casing integrally form an assembling unit;and a cooling fin which mounts rectifying elements and which isconfigured into a circular ring shape separated at a cutout section, thecooling fin being disposed so that the regulator, the brush container,and the connector casing are disposed in the cutout section, wherein aclearance is provided between the brush container and the regulator soas to serve as the cooling air passage, and the connector casing ispositioned radially outward of the regulator, and a clearance isprovided between the connector casing and the regulator as a furthercooling air passage.